This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | -9 |
| 4 | 27 |
| 5 | -54 |
| 6 | 99 |
| 7 | -189 |
| 8 | 378 |
| 9 | -765 |
| 10 | 1539 |
| 11 | -3078 |
| 12 | 6147 |
| 13 | -12285 |
| 14 | 24570 |
| 15 | -49149 |
| 16 | 98307 |
| 17 | -196614 |
| 18 | 393219 |
| 19 | -786429 |
| 20 | 1572858 |
| 21 | -3145725 |
| 22 | 6291459 |
| 23 | -12582918 |
| 24 | 25165827 |
| 25 | -50331645 |
| 26 | 100663290 |
| 27 | -201326589 |
| 28 | 402653187 |
| 29 | -805306374 |
| 30 | 1610612739 |
| 31 | -3221225469 |
| 32 | 6442450938 |